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1 | /* | |
2 | * linux/kernel/futex_compat.c | |
3 | * | |
4 | * Futex compatibililty routines. | |
5 | * | |
6 | * Copyright 2006, Red Hat, Inc., Ingo Molnar | |
7 | */ | |
8 | ||
9 | #include <linux/linkage.h> | |
10 | #include <linux/compat.h> | |
11 | #include <linux/nsproxy.h> | |
12 | #include <linux/futex.h> | |
13 | ||
14 | #include <asm/uaccess.h> | |
15 | ||
16 | ||
17 | /* | |
18 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: | |
19 | */ | |
20 | static inline int | |
21 | fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry, | |
22 | compat_uptr_t __user *head, unsigned int *pi) | |
23 | { | |
24 | if (get_user(*uentry, head)) | |
25 | return -EFAULT; | |
26 | ||
27 | *entry = compat_ptr((*uentry) & ~1); | |
28 | *pi = (unsigned int)(*uentry) & 1; | |
29 | ||
30 | return 0; | |
31 | } | |
32 | ||
33 | static void __user *futex_uaddr(struct robust_list __user *entry, | |
34 | compat_long_t futex_offset) | |
35 | { | |
36 | compat_uptr_t base = ptr_to_compat(entry); | |
37 | void __user *uaddr = compat_ptr(base + futex_offset); | |
38 | ||
39 | return uaddr; | |
40 | } | |
41 | ||
42 | /* | |
43 | * Walk curr->robust_list (very carefully, it's a userspace list!) | |
44 | * and mark any locks found there dead, and notify any waiters. | |
45 | * | |
46 | * We silently return on any sign of list-walking problem. | |
47 | */ | |
48 | void compat_exit_robust_list(struct task_struct *curr) | |
49 | { | |
50 | struct compat_robust_list_head __user *head = curr->compat_robust_list; | |
51 | struct robust_list __user *entry, *next_entry, *pending; | |
52 | unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; | |
53 | unsigned int uninitialized_var(next_pi); | |
54 | compat_uptr_t uentry, next_uentry, upending; | |
55 | compat_long_t futex_offset; | |
56 | int rc; | |
57 | ||
58 | if (!futex_cmpxchg_enabled) | |
59 | return; | |
60 | ||
61 | /* | |
62 | * Fetch the list head (which was registered earlier, via | |
63 | * sys_set_robust_list()): | |
64 | */ | |
65 | if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi)) | |
66 | return; | |
67 | /* | |
68 | * Fetch the relative futex offset: | |
69 | */ | |
70 | if (get_user(futex_offset, &head->futex_offset)) | |
71 | return; | |
72 | /* | |
73 | * Fetch any possibly pending lock-add first, and handle it | |
74 | * if it exists: | |
75 | */ | |
76 | if (fetch_robust_entry(&upending, &pending, | |
77 | &head->list_op_pending, &pip)) | |
78 | return; | |
79 | ||
80 | next_entry = NULL; /* avoid warning with gcc */ | |
81 | while (entry != (struct robust_list __user *) &head->list) { | |
82 | /* | |
83 | * Fetch the next entry in the list before calling | |
84 | * handle_futex_death: | |
85 | */ | |
86 | rc = fetch_robust_entry(&next_uentry, &next_entry, | |
87 | (compat_uptr_t __user *)&entry->next, &next_pi); | |
88 | /* | |
89 | * A pending lock might already be on the list, so | |
90 | * dont process it twice: | |
91 | */ | |
92 | if (entry != pending) { | |
93 | void __user *uaddr = futex_uaddr(entry, futex_offset); | |
94 | ||
95 | if (handle_futex_death(uaddr, curr, pi)) | |
96 | return; | |
97 | } | |
98 | if (rc) | |
99 | return; | |
100 | uentry = next_uentry; | |
101 | entry = next_entry; | |
102 | pi = next_pi; | |
103 | /* | |
104 | * Avoid excessively long or circular lists: | |
105 | */ | |
106 | if (!--limit) | |
107 | break; | |
108 | ||
109 | cond_resched(); | |
110 | } | |
111 | if (pending) { | |
112 | void __user *uaddr = futex_uaddr(pending, futex_offset); | |
113 | ||
114 | handle_futex_death(uaddr, curr, pip); | |
115 | } | |
116 | } | |
117 | ||
118 | asmlinkage long | |
119 | compat_sys_set_robust_list(struct compat_robust_list_head __user *head, | |
120 | compat_size_t len) | |
121 | { | |
122 | if (!futex_cmpxchg_enabled) | |
123 | return -ENOSYS; | |
124 | ||
125 | if (unlikely(len != sizeof(*head))) | |
126 | return -EINVAL; | |
127 | ||
128 | current->compat_robust_list = head; | |
129 | ||
130 | return 0; | |
131 | } | |
132 | ||
133 | asmlinkage long | |
134 | compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr, | |
135 | compat_size_t __user *len_ptr) | |
136 | { | |
137 | struct compat_robust_list_head __user *head; | |
138 | unsigned long ret; | |
139 | const struct cred *cred = current_cred(), *pcred; | |
140 | ||
141 | if (!futex_cmpxchg_enabled) | |
142 | return -ENOSYS; | |
143 | ||
144 | if (!pid) | |
145 | head = current->compat_robust_list; | |
146 | else { | |
147 | struct task_struct *p; | |
148 | ||
149 | ret = -ESRCH; | |
150 | rcu_read_lock(); | |
151 | p = find_task_by_vpid(pid); | |
152 | if (!p) | |
153 | goto err_unlock; | |
154 | ret = -EPERM; | |
155 | pcred = __task_cred(p); | |
156 | /* If victim is in different user_ns, then uids are not | |
157 | comparable, so we must have CAP_SYS_PTRACE */ | |
158 | if (cred->user->user_ns != pcred->user->user_ns) { | |
159 | if (!ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE)) | |
160 | goto err_unlock; | |
161 | goto ok; | |
162 | } | |
163 | /* If victim is in same user_ns, then uids are comparable */ | |
164 | if (cred->euid != pcred->euid && | |
165 | cred->euid != pcred->uid && | |
166 | !ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE)) | |
167 | goto err_unlock; | |
168 | ok: | |
169 | head = p->compat_robust_list; | |
170 | rcu_read_unlock(); | |
171 | } | |
172 | ||
173 | if (put_user(sizeof(*head), len_ptr)) | |
174 | return -EFAULT; | |
175 | return put_user(ptr_to_compat(head), head_ptr); | |
176 | ||
177 | err_unlock: | |
178 | rcu_read_unlock(); | |
179 | ||
180 | return ret; | |
181 | } | |
182 | ||
183 | asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val, | |
184 | struct compat_timespec __user *utime, u32 __user *uaddr2, | |
185 | u32 val3) | |
186 | { | |
187 | struct timespec ts; | |
188 | ktime_t t, *tp = NULL; | |
189 | int val2 = 0; | |
190 | int cmd = op & FUTEX_CMD_MASK; | |
191 | ||
192 | if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || | |
193 | cmd == FUTEX_WAIT_BITSET || | |
194 | cmd == FUTEX_WAIT_REQUEUE_PI)) { | |
195 | if (get_compat_timespec(&ts, utime)) | |
196 | return -EFAULT; | |
197 | if (!timespec_valid(&ts)) | |
198 | return -EINVAL; | |
199 | ||
200 | t = timespec_to_ktime(ts); | |
201 | if (cmd == FUTEX_WAIT) | |
202 | t = ktime_add_safe(ktime_get(), t); | |
203 | tp = &t; | |
204 | } | |
205 | if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || | |
206 | cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP) | |
207 | val2 = (int) (unsigned long) utime; | |
208 | ||
209 | return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); | |
210 | } |